projects\01\Mux.hdl - Not always returns 1

projects\01\Mux.hdl - Not always returns 1

Hi,

I've written Not, And, Or, Xor. They've all passed the tests successfully. Some of them even use Not as a part, no problem there.

Now I've come to writing Mux and when I use Not it always returns 1 (regardless of the input). I've even tried using the built-in Not and it also return 1 all the time.
I have a feeling that something is wrong with my Mux file, but I just can't pinpoint it.

This is the Mux implementation:

// This file is part of www.nand2tetris.org
// and the book "The Elements of Computing Systems"
// by Nisan and Schocken, MIT Press.
// File name: projects/01/Mux.hdl